Molecular pathology of colorectal cancer

The identification of several types of familial colorectal cancer has led t o the discovery of some of the genes involved in these diseases. It was sub sequently shown that somatic mutations of these genes (APC, mismatch repair genes, TP53, KRAS, and DCC) also occur in sporadic colorectal cancer. Grad ually, this molecular information is being incorporated into the standard h istopathological analysis of colorectal cancer and can be used for the char acterization of primary tumors. Although attempts have been made to use mol ecular parameters to better define dysplasia grades, differentiate between adenoma and carcinoma, and subtype carcinomas, histological parameters rema in the standard for the classification of primary tumors. Nonetheless, mole cular parameters may help define subgroups of colorectal carcinoma differin g in prognosis and requiring individualized treatment regimens. Interesting possibilities are predicting the response to chemotherapy or radiotherapy at a molecular level and the search for metastasis by looking for molecular markers in lymph nodes or circulating blood. Other pathological tests bein g developed include the detection of KRAS, TP53, or APC mutations in stool and plasma. Such approaches will have a significant impact on the clinical management of colorectal cancer.